JP2023512495A - Lithium extraction method - Google Patents

Abstract

A lithium extraction method comprising the steps of: preparing lithium phosphate containing impurities; dissolving said lithium phosphate and impurities in acid; said lithium phosphate and impurities dissolved in acid adding an additive to the solution to obtain a lithium-containing solution, wherein the additive is a substance that precipitates phosphate anions and impurities at the same time, and the lithium-containing solution obtained by the additive. can provide a lithium extraction method that is basic. [Selection drawing] Fig. 1

Description

The present invention relates to lithium extraction methods.

In recent years, lithium secondary batteries have been widely used not only as a power source for mobile phones, notebook computers, and other IT devices, but also as a power source for electric vehicles. Electricity storage systems for renewable energy and new renewable energy will be greatly activated, and demand for them is expected to soar.

Lithium is mainly used in the form of lithium carbonate (Li ₂ CO ₃ ) as a raw material for cathode materials, anode materials, and electrolytes, which are important parts of electric vehicles and electricity storage systems. Therefore, in order to inexpensively manufacture electric vehicles and electric storage systems, for which demand is expected to increase significantly, and to smoothly supply them to the market, it is necessary to develop a technique for economically manufacturing lithium carbonate.

Lithium carbonate is generally produced after naturally evaporating natural brine containing lithium about 0.2 g/L to 1.5 g/L and concentrating lithium to a high concentration of about 60 g/L. and depositing carbonate in the form of lithium carbonate (Li ₂ CO ₃ ). However, due to the high solubility of lithium carbonate (13 g/L), in order to concentrate lithium to about 60 g/L, it is necessary to evaporate and concentrate salt water over a long period of time of one year or more. of lithium is deposited and lost.

To solve these problems, a lithium phosphate (Li ₃ PO ₄ ) extraction method that can minimize the natural evaporation process has been developed (Korea Registered Patent No. 10-1363342). When extracting lithium in the form of lithium phosphate using the lithium phosphate extraction method, the low solubility (0.39 g/L) characteristic of lithium phosphate eliminates the process of evaporation and concentration of salt water over a long period of time. Not only can the time be shortened, but the loss of lithium generated in the evaporation/concentration process can be suppressed, and lithium can be extracted with a high recovery rate. However, as described above, lithium phosphate must be converted to lithium carbonate in order to be used as a raw material for lithium secondary batteries.

In recent years, a low-concentration lithium hydroxide solution with a lithium concentration of 5 g/L or less was prepared by mixing Ca(OH) ₂ with a lithium phosphate-water suspension (slurry) at a high temperature (90 ° C. or higher). A technology has been developed in which a high-concentration lithium hydroxide solution having a lithium concentration of 30 g/L or more is prepared by evaporation and concentration, and then carbon dioxide (CO ₂ ) gas is introduced to produce lithium carbonate.

However, when lithium phosphate is converted to lithium carbonate by this method, the lithium phosphate suspension must be heated to a high temperature and reacted for a long time, and the low-concentration lithium hydroxide solution is evaporated. - Since it must be concentrated, there is a problem of increased energy costs (Korea Registered Patent No. 10-1405486).

Also, after dissolving lithium phosphate in acid to produce a lithium solution having a lithium concentration of 0.05 g/L to 0.16 g/L, divalent alkaline earth metal ions and phosphorus are removed using an ion exchange resin. A method for producing lithium carbonate by reacting an aqueous solution of lithium hydroxide having a lithium concentration of 3.5 g/L to 4.5 g/L, which is obtained by removing and using bipolar electrodialysis, with carbon dioxide gas. It has been developed.

However, when producing lithium carbonate by this method, the lithium concentration in the lithium solution is too low, so the lithium recovery rate is low. However, there is a problem that the manufacturing cost is greatly increased due to this (Korea Registered Patent No. 10-1888181).

On the other hand, lithium phosphate-metal compound (one of iron, copper, lead, zinc, manganese, calcium, cerium, yttrium, or lanthanum compound) mixed suspension is added with acid and dissolved, then hydroxylated. A method of producing lithium carbonate by adding alkali to prepare a high-concentration lithium solution from which metals and phosphorus have been removed by adjusting the pH to 1 to 10 and adding carbonate to the solution has been developed. . However, using such a method increases the amount of acid used to dissolve all of the lithium phosphate and metal compound. In addition, when adding an alkali to induce the deposition of metal ions present in the acidic solution in which lithium phosphate is dissolved, the pH of the reaction solution is limited to 1 to 10 so that the heavy metal ions can be completely removed. After dissolving the lithium phosphate-metal compound mixture, the pH is adjusted by adding alkali, which complicates the process, increases the amount of raw materials and auxiliary raw materials used, and is economical. decreases (Japanese registered patents JP5632169B2 and JP5528153B2).

As described above, when using the lithium carbonate production method using lithium phosphate developed so far, the lithium recovery rate is low, the energy cost and equipment investment cost are high, the raw material and auxiliary raw material costs are excessive, and the process is complicated. Therefore, there is a problem that the economic efficiency is lowered. Therefore, there is an urgent need for development of a technology that can economically produce lithium carbonate using lithium phosphate.

Therefore, the present invention provides a method for extracting lithium with a high lithium recovery rate.

In addition, the method requires less energy consumption, raw material/auxiliary raw material costs, and equipment investment costs, and the process is simple, so that a lithium compound can be economically produced from lithium phosphate.

In one embodiment of the present invention, preparing lithium phosphate containing impurities; dissolving the lithium phosphate and impurities in acid; and dissolving the lithium phosphate and impurities in acid. adding an additive to obtain a lithium-containing solution, wherein the additive is a substance that precipitates phosphate anions and impurities at the same time, and the lithium-containing solution obtained by the additive is a base A method for extracting lithium is provided.

The impurities may include alkaline earth metals.

The alkaline earth metal may be beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), or combinations thereof.

The lithium concentration in the solution in which the lithium phosphate and impurities are dissolved in acid may range from 10 g/L to 35 g/L.

In the step of dissolving the lithium phosphate and impurities in acid, the acid may be hydrochloric acid, hypochlorous acid, nitric acid, acetic acid, or a combination thereof.

The pH of the solution obtained by dissolving the lithium phosphate and impurities in acid may range from -0.1 to 4.5.

The additive may be an oxide or a hydroxide.

The additive may be a cationic oxide or hydroxide of beryllium, magnesium, calcium, strontium, barium, radium, or combinations thereof.

More specifically, the additive may be calcium hydroxide (Ca(OH) ₂ ), magnesium hydroxide (Mg(OH) ₂ ), or a combination thereof.

Phosphate anions and impurities can thereby be deposited in the form of sparingly soluble precipitates.

The poorly soluble precipitates include hydroxylapatite (Ca ₅ (PO ₄ ) ₃ OH), brushite (CaHPO ₄ .2H ₂ O), amorphous calcium-phosphorus compounds, calcium hydroxide, newberyite ( Newberyite, MgHPO ₄ .3H ₂ O), Magnesium phosphate (Mg ₃ (PO ₄ ) ₂ ) amorphous magnesium-phosphorus compounds and magnesium hydroxide or mixtures thereof.

In the step of adding an additive to the solution in which the lithium phosphate and impurities are dissolved in acid to obtain the lithium-containing solution, the obtained lithium-containing solution may have a pH of 9 or higher.

In the step of adding an additive to the solution in which the lithium phosphate and impurities are dissolved in acid to obtain the lithium-containing solution, the obtained lithium-containing solution may have a pH of 11 or more.

Lithium carbonate can be obtained by adding a carbonic acid-providing material to the obtained lithium-containing solution.

The carbonation-providing substances include sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), ammonium carbonate ((NH ₄ ) ₂ CO ₃ ), sodium bicarbonate (NaHCO ₃ ), potassium bicarbonate (KHCO ₃ ) or a combination thereof.

The method may further include washing and drying the obtained lithium carbonate.

An embodiment of the present invention provides a method for extracting lithium from lithium phosphate containing impurities (more specifically, alkaline earth metals), which provides a high lithium recovery rate and low raw material/auxiliary raw material and energy consumption. and equipment costs, lithium compounds (eg, lithium carbonate) can be produced economically.

FIG. 1 and Table 1 show that 10 g of magnesium-containing lithium phosphate and 0.1 L of each hydrochloric acid aqueous solution with different acidity were mixed at room temperature to produce a high-concentration lithium solution with a lithium concentration of 10 g/L. The pH and lithium concentration of the reaction filtrate obtained by filtration after stirring for 60 minutes are shown. Table 2 shows that a magnesium-containing lithium phosphate solution having a pH of 4.33 was prepared by adding 10 g of lithium phosphate containing magnesium to 0.1 L of a hydrochloric acid aqueous solution at room temperature, and 2.3 g to 2.3 g of calcium hydroxide was added to each solution. After adding 23.8 g, stirring and filtering for 2 hours, the contents of chemical components and pH of the reaction filtrate obtained are shown. FIG. 2 shows that 10 g of magnesium-containing lithium phosphate is added to 0.1 L of hydrochloric acid aqueous solution at room temperature to prepare a pH 4.33 magnesium-containing lithium phosphate solution, and 2.3 g to 2.3 g of calcium hydroxide is added to each solution. The X-ray diffraction pattern of the precipitate obtained after charging 23.8 g, stirring, filtering, washing and drying for 2 hours is shown. FIG. 3 shows the precipitation obtained by adding 6.478 g of Na ₂ CO ₃ to 0.1 L of lithium phosphate solution at room temperature from which magnesium and phosphorus have been removed, stirring, filtering, washing and drying for 2 hours. 1 shows the X-ray diffraction pattern of the product.

Many embodiments of the present invention will now be described in detail so that those skilled in the art can easily implement the present invention. This invention may be embodied in many different forms and is not limited to the embodiments set forth herein.

In order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals are used throughout the specification for the same or similar components.

Also, throughout the specification, when a part "includes" a component, this does not exclude other components, unless specifically stated to the contrary. It is meant to include further.

In one embodiment of the present invention, preparing lithium phosphate containing impurities; dissolving the lithium phosphate and impurities in acid; dissolving the lithium phosphate and impurities in acid; adding an additive to the liquid to obtain a lithium-containing solution, wherein the additive is a substance that precipitates phosphate anions and impurities at the same time, and the lithium-containing solution obtained by the additive is A lithium extraction method is provided that is basic.

An embodiment of the present invention dissolves lithium phosphate containing impurities (e.g., alkaline earth metals) at room temperature using a hydrochloric acid solution, which is an example of the acid solution, thereby dissolving high-concentration lithium phosphate. A method for removing impurities and phosphorus by obtaining a liquid and adding calcium hydroxide, which is an example of the additive, at room temperature will be described in detail.

In a subsequent step, lithium carbonate is obtained by adding an example of a carbonate, sodium carbonate, to the obtained lithium-containing solution at room temperature; A method for economically producing lithium carbonate by drying is described.

The dissolution of lithium phosphate containing impurities (magnesium, which is a type of alkaline earth metal) with the hydrochloric acid aqueous solution according to one embodiment of the present invention may be performed according to Reaction Formula 1 below.

[Reaction Formula 1]
(Mg, Li)PO ₄ +2HCl+3H ₂ O→Li ⁺ +Mg ²⁺ +H ₂ PO ₄ ⁻ +2Cl ⁻ +3H ₂ O

That is, the magnesium-containing lithium phosphate is dissolved in hydrochloric acid at room temperature to be converted into a lithium phosphate solution containing Li ⁺ , Mg ²⁺ , H ₂ PO ₄ ⁻ , and Cl ⁻ .

Specific examples of the acid for dissolving the lithium phosphate may be hydrochloric acid, hypochlorous acid, nitric acid, acetic acid, or combinations thereof. Sulfuric acid can react with alkaline earth metals such as calcium to form precipitates and generate acid sludge. It is preferably not used to reduce cleanup costs. However, a portion of sulfuric acid may be selectively used depending on the combination of various impurities.

The solubility of the lithium carbonate is 13 g/L, which is 2.5 g/L in terms of lithium concentration. Therefore, the lithium concentration of the lithium phosphate solution must be 10 g/L or more in order to obtain a high lithium recovery rate of 75% or more when lithium carbonate is deposited from the lithium phosphate solution.

Therefore, in the present invention, the lithium concentration of the lithium phosphate solution is limited to 10 g/L or more. On the other hand, when the lithium concentration of the lithium phosphate solution is 30 g/L, the lithium recovery rate is 91.7%, which is more preferable.

As shown in the examples below, in order to obtain a lithium phosphate solution with a lithium concentration of 10 g/L or more, the pH of the reaction solution obtained by mixing lithium phosphate and an acid aqueous solution is 4.5 or less. There must be. This will be described in more detail in the embodiments below.

The removal of alkaline earth metals and phosphorus according to an embodiment of the present invention may proceed according to Reaction Formula 2 or Reaction Formula 3 below.

[Reaction Formula 2]
Li ⁺ +Mg ²⁺ +H ₂ PO ₄ ⁻ +2Cl ⁻ +3H _{2 O} +Ca(OH) ₂ →Li ⁺ +H ⁺ +2Cl ⁻ +Mg(OH) ₂ ⁺ CaHPO 4.2H ₂ O+H ₂ O

[Reaction Formula 3]
3Li ⁺ +3Mg ²⁺ +3H ₂ PO ₄ ⁻ +6Cl ⁻ +9H ₂ O+5Ca(OH) ₂ →3Li ⁺ +Cl ⁻ +2OH ⁻ +3Mg(OH) ₂ +Ca ₅ (PO ₄ ) _3.OH +10H ₂ O+5HCl(g)

The additive for removing the alkaline earth metal and phosphorus is a hydroxide ion (OH ⁻ ) that reacts with phosphorus at room temperature to produce a sparingly soluble compound and simultaneously produces a sparingly soluble compound with the alkaline earth metal. It may be a substance that generates As a result, phosphorus and the alkaline earth metal impurities can be deposited at the same time.

More specifically, the additive may be an alkaline earth metal oxide or hydroxide.

As a specific example, the additive cation may be beryllium, magnesium, calcium, barium, radium, or a combination thereof, and the additive may be an oxide or hydroxide thereof. .

For example, the additive may be calcium hydroxide, magnesium hydroxide, or a combination thereof, or alternatively calcium oxide or magnesium oxide.

For example, calcium carbonate (CaCO ₃ ) or magnesium carbonate (MgCO ₃ ) can be heated to obtain calcium oxide or magnesium oxide. When water is added to the calcium oxide or magnesium oxide obtained from this, calcium hydroxide and magnesium hydroxide can be obtained.

In order to remove impurities (eg, alkaline earth metal) and phosphorus from the lithium phosphate solution containing the impurity (eg, alkaline earth metal), calcium hydroxide, which is an example of an additive, is added at room temperature. may be

In said specific example, magnesium may be precipitated in the form of sparingly soluble magnesium hydroxide, and phosphorus may be precipitated from sparingly soluble hydroxylapatite ( _Ca5 ( _PO4 ) ₃ -OH) or brushite (CaHPO). _{4.2H 2} O). These may be filtered off from the lithium phosphate solution.

The amount of the additive added may be 1 equivalent or more with respect to the phosphorus content in order to completely remove the phosphorus present in the lithium phosphate solution. When the above range is satisfied, not only phosphorus can be completely removed, but also the reaction rate can be improved.

The amount of the additive added is such that the pH of the lithium phosphate solution is adjusted to 9 or more, or preferably 11 or more so that the alkaline earth metal and phosphorus present in the lithium phosphate solution can be precipitated and completely removed. It may be an input amount that can be maintained.

The preparation of lithium carbonate according to an embodiment of the present invention may proceed according to Reaction Scheme 4 below.

In order to precipitate lithium carbonate from the room temperature lithium-containing solution from which the alkaline earth metal and phosphorus have been removed according to an embodiment of the present invention, sodium carbonate, which is an example of a carbonic acid supply material, may be added.

[Reaction Formula 4]
6Li ⁺ +2Cl ⁻ +4OH ⁻ +20H ₂ O+3Na ₂ CO ₃ →3Li ₂ CO ₃ +6Na ⁺ +2Cl ⁻ +4OH ⁻ +20H ₂ O

That is, the sodium carbonate reacts with lithium at room temperature to generate and deposit lithium carbonate. In addition, when one equivalent or more of the lithium-containing solution from which alkaline earth metals and phosphorus have been removed is added, lithium carbonate can be obtained with a high recovery rate of 75% or more.

Specific examples of the carbonate are sodium carbonate, potassium carbonate, ammonium carbonate and the like.

More specifically, the carbonate may be sodium bicarbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, ammonium carbonate, or combinations thereof.

The amount of the lithium carbonate added may be 1 equivalent or more with respect to the lithium content of the lithium-containing solution. If the above range is satisfied, it may be advantageous in terms of reaction rate.

In the present specification, room temperature does not mean a constant temperature, but means a temperature without the addition of external energy. Therefore, the normal temperature may change depending on the place and time.

The present invention will now be described with reference to specific examples. However, the claims of the present invention are not limited to the following examples.

[Example 1]
In order to prepare a high-concentration lithium solution with a lithium concentration of 10 g/L, 10 g of magnesium-containing lithium phosphate and 0.1 L of hydrochloric acid aqueous solution with different acidity were mixed at room temperature and then stirred for 60 minutes.

After the stirring was completed, each reaction solution was filtered, and the pH and lithium concentration were measured, and the results are shown in FIG. 1 and Table 1.

As shown in FIG. 1, as the pH of the reaction solution decreased, lithium phosphate was dissolved and the lithium concentration gradually increased. When the pH of the reaction filtrate reaches 4.5 or less, the lithium concentration is about 10 g/L, and even when the pH of the reaction filtrate is reduced to 4.5 or less, the lithium concentration does not increase any more. I found out.

From this, it can be seen that all of the charged lithium phosphate is dissolved when the pH of the reaction filtrate is 4.5 or less. On the other hand, when the pH of the reaction filtrate is too low as -1.0 or less, lithium phosphate can be completely dissolved, but there is a problem that the amount of hydrochloric acid used is excessively increased.

[Example 2]
10 g of magnesium-containing lithium phosphate was added to 0.1 L of a hydrochloric acid aqueous solution at room temperature and stirred for 1 hour to prepare a magnesium-containing lithium phosphate solution having a pH of 4.33.

2.3 g to 23.8 g of calcium hydroxide was added to each of the lithium phosphate solutions, stirred for 2 hours, and precipitates were filtered.

As shown in Table 2 below, when the pH of the reaction filtrate is 11 or more, phosphorus and magnesium are completely removed. Phosphorus and magnesium can be completely removed even when a large amount of calcium hydroxide is added to increase the pH of the reaction solution to 14 or more, but the cost of raw materials and auxiliary raw materials increases, and unreacted precipitates Since the presence of inter-layer water reduces the lithium recovery rate, it is preferable to control the pH of the lithium phosphate solution containing the alkaline earth metal oxide or hydroxide to 11 to 14 or less.

On the other hand, the precipitate filtered from the reaction solution was washed with tap water and then dried at 105° C. for 24 hours. FIG. 2 shows the results of analyzing the mineral phase of the precipitate, which showed a reaction solution pH of 11.35, using an X-ray diffraction analyzer.

As shown in FIG. 2, magnesium is precipitated in the form of sparingly soluble magnesium hydroxide, phosphorus is mostly precipitated in the form of sparingly soluble hydroxylapatite, and partly in the form of lithium phosphate. completely removed from the lithium acid solution.

[Example 3]
64.78 g of Na ₂ CO ₃ was added to 1 L of the room temperature lithium-containing solution from which magnesium and phosphorus had been removed, and the mixture was stirred for 2 hours to react, and the precipitate was filtered.

The precipitate filtered from the reaction solution was washed with tap water, dried at 105° C. for 24 hours, and analyzed for mineral phases using an X-ray diffraction analyzer. The analytical results are shown in FIG. As shown in FIG. 3, the precipitate was observed as a lithium carbonate single phase, indicating that lithium carbonate was successfully synthesized.

The present invention is not limited to the above embodiments, and can be manufactured in various forms different from each other. It will be understood that it may be embodied in other specific forms without changing the specific features. Therefore, it should be understood that each embodiment described above is illustrative in all respects and not restrictive.

Claims (12)

providing lithium phosphate containing impurities;
dissolving the lithium phosphate and impurities in acid;
adding an additive to the solution in which the lithium phosphate and impurities are dissolved in acid to obtain a lithium-containing solution;
The method for extracting lithium, wherein the additive is a substance that precipitates phosphate anions and impurities at the same time, and the lithium-containing solution obtained by the additive is basic. 2. The method of extracting lithium according to claim 1, wherein said impurities comprise alkaline earth metals. 3. The lithium of claim 2, wherein the alkaline earth metal is beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), or combinations thereof. Extraction method. 2. The method for extracting lithium according to claim 1, wherein the solution of lithium phosphate and impurities in acid has a lithium concentration of 10 g/L to 35 g/L. In dissolving the lithium phosphate and impurities in acid,
2. The method of extracting lithium according to claim 1, wherein the acid is hydrochloric acid, hypochlorous acid, nitric acid, acetic acid or a combination thereof. 2. The method for extracting lithium according to claim 1, wherein the pH of the solution obtained by dissolving the lithium phosphate and impurities in acid is -0.1 to 4.5. 2. The lithium extraction method according to claim 1, wherein the additive is an oxide or a hydroxide. 8. The lithium extraction method of claim 7, wherein the additive is a cation oxide or hydroxide of beryllium, magnesium, calcium, strontium, barium, radium or combinations thereof. In the step of adding an additive to the solution in which the lithium phosphate and impurities are dissolved in an acid to obtain a lithium-containing solution,
The method for extracting lithium according to claim 1, wherein the obtained lithium-containing solution has a pH of 9 or higher. In the step of adding an additive to the solution in which the lithium phosphate and impurities are dissolved in an acid to obtain a lithium-containing solution,
2. The method for extracting lithium according to claim 1, wherein the obtained lithium-containing solution has a pH of 11 or higher. 2. The method for extracting lithium according to claim 1, wherein a carbonic acid-providing substance is added to the obtained lithium-containing solution to obtain lithium carbonate. The carbonation-providing substances include sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), ammonium carbonate ((NH ₄ ) ₂ CO ₃ ), sodium bicarbonate (NaHCO ₃ ), potassium bicarbonate (KHCO ₃ ) or a combination thereof.

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